////
//// Created by shenlf on 2021-10-30.
////
//#include <iostream>
//using namespace std;
//int main(){
//    unsigned u = 10, u2 = 42;
//    cout << u2 - u << endl;
//    cout << u - u2 << endl;
//    int i = 10, i2 = 42;
//    cout << i2 - i << endl;
//    cout << i - i2 << endl;
//    cout << i - u << endl;
//    cout << u - i << endl;
//    unsigned c = -1;
//    cout << c << endl;
//    return 0;
//}
//
